1. Technical Field
The present invention relates to a thermal head and a thermal head unit, which are used, for instance, in a miniature portable recording apparatus, a facsimile machine, a printer for tickets and receipts, etc, and also relates to a method of manufacturing the thermal head and the thermal head unit.
2. Background Art
A thermal head includes a head chip in which heating elements arrayed in a row and electrodes connected to these elements are provided on a ceramic substrate, and an IC chip serving as a driver for outputting print signals to selectively generate heat from desired heating elements at desired timings.
FIG. 19 shows an example of a thermal head unit in which the thermal head of this type is mounted onto a heat radiating plate to form a unit. The thermal head unit includes a thermal head 101, and a heat radiating plate 102 made of aluminum or the like. The thermal head 101 is designed such that an electrode 104 and a heating element 105 are formed on a ceramic substrate 103, and an IC chip 106 is further mounted thereon. The electrode 104, a separately provided external terminal 107 for inputting external signals therein, and the IC chip 106.are connected together through bonding wires 108. The IC chip 106 and the bonding wires 108 are molded with sealing resin 109.
To form aboard for the thermal head 101 of this type, a relatively large ceramic substrate 103 is used, and the electrodes 104, the heating elements 105 and the like are formed as thin or thick films on the substrate 103. For this reason, the board obtained by one board forming process is low in number, and thus the productivity is low.
To improve the productivity of the board forming process, it known to provide a composite substrate using a ceramic substrate reduced in size. That is, as shown in FIG. 20, in place of the ceramic substrate 103, a ceramic circuit board 103A and a wiring substrate 103B such as a glass fabric based epoxy resin substrate (hereafter referred to as GE substrate when applicable) are used. In this case, the external terminal 107 is provided on the wiring substrate 103B.
Although this approach makes it possible to improve the productivity of the board forming process, the handling ability is considerably reduced since the ceramic substrate 103A and the wiring substrate 103B are joined to the heat radiating plate 102, and then the IC chip 106 is mounted thereon and the wire bonding is carried out therefor.
In view of the above problems, an object of the present invention is to provide a thermal head, a thermal head unit and a method of manufacturing the same, which can improve the productivity of a board forming process while improving the handling ability of a mounting process, thereby remarkably reducing the cost.
According to a first aspect of the present invention, to solve the above problems, a thermal head is characterized by comprising a head chip having one surface on which heating elements and electrodes connected to the heating elements are provided, and a semiconductor integrated circuit connected to the electrodes, the thermal head characterized in that a wiring substrate is provided, which is joined to the other surface of the head chip, and the semiconductor integrated circuit is mounted to the wiring substrate.
According to a second aspect of the present invention, in the first aspect of the invention, a thermal head is characterized in that one end side of the head chip in a width direction thereof is protruded from the wiring substrate.
According to a third aspect of the present invention, in the second aspect of the invention, a thermal head is characterized in that a protruded amount by which the head chip is protruded from the wiring substrate is 20% to 70% of a width of the head chip.
According to a fourth aspect of the present invention, in the first aspect of the invention, a thermal head is characterized in that the head chip is completely overlapped with and joined onto the wiring substrate.
According to a fifth aspect of the present invention, in the fourth aspect of the invention, a thermal head is characterized in that one end side of the wiring substrate is protruded from one end side of the head chip in a width direction thereof.
According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the invention, a thermal head is characterized in that the semiconductor integrated circuit is mounted onto the wiring substrate to be substantially contacted with an end face of the head chip.
According to a seventh aspect of the present invention, in any one of the first to sixth aspects of the invention, a thermal head is characterized in that a height of a surface of the semiconductor integrated circuit is substantially the same as a height of a surface of the head chip.
According to an eighth aspect of the present invention, in any one of the first to sixth aspects of the invention, a thermal head is characterized in that a height of a surface of the semiconductor integrated circuit is lower than a height of a surface of the head chip.
According to a ninth aspect of the present invention, in any one of the first to eighth aspects of the invention, a thermal head is characterized in that a common electrode is provided, which extends in a longitudinal direction along an end portion of the head chip opposite from the heating elements in a width direction, and connection wirings connecting the common electrode to common electrode wirings provided to the wiring substrate are provided at plural locations in the longitudinal direction.
According to a tenth aspect of the present invention, in the ninth aspect of the invention, a thermal head is characterized in that each of the connection wirings connecting the common electrode provided to the head chip to the common electrode wirings provided to the wiring substrate are provided between physical blocks defined by the semiconductor integrated circuits.
According to an eleventh aspect of the present invention, in the tenth aspect of the invention, a thermal head is characterized in that the connection wirings connecting the common electrode provided to the head chip to the common electrode wirings provided to the wiring substrate are provided for the respective physical blocks defined by the semiconductor integrated circuits.
According to a twelfth aspect of the present invention, in the any one of the ninth to eleventh aspects of the invention, a thermal head is characterized in that at least one connection wiring connecting the common electrode provided to the head chip to a common electrode wiring provided to the wiring substrate is provided within the physical block defined by the semiconductor integrated circuit.
According to a thirteenth aspect of the present invention a thermal head unit is characterized in that the thermal head in any one of the first to twelfth aspects is mounted to a support member.
According to a fourteenth aspect of the present invention, in the thirteenth aspect of the invention, a thermal head unit is characterized in that one end portion of the head chip in the width direction, which serves as a heating element forming portion, is protruded from the wiring substrate, the support member is formed with an upper step portion to which the heating element forming portion is joined, and a step difference portion recessed more deeply than a thickness of the wiring substrate, and an adhesive agent layer is provided in a clearance that is formed between the step difference portion and the wiring substrate when the heating element forming portion of the head chip is joined to the upper step portion.
According to a fifteenth aspect of the present invention, in the fourteenth aspect of the invention, a thermal head unit is characterized in that an adhesive layer is provided for joining the heating element forming portion of the head chip to the upper step portion, and the adhesive agent layer is softer than the adhesive layer after the heating element forming portion is joined to the upper step portion and before the adhesive agent layer is hardened.
According to a sixteenth aspect of the present invention, in any one of the fourteenth to sixteenth aspect of the invention, a thermal head unit is characterized in that an adhesive layer is provided for joining the heating element forming portion of the head chip to the upper step portion, and the adhesive agent layer is thicker than the adhesive layer.
According to a seventeenth aspect of the present invention, in any one of the fourteenth to sixteenth aspect of the invention, a thermal head unit is further characterized in that at least one recessed groove is provided to a bottom portion of the step difference portion.
According to an eighteenth aspect of the present invention, a method of manufacturing a thermal head comprising a ceramic substrate having one surface on which heating elements and electrodes connected to the heating elements are provided, and a wiring substrate joined to the other surface of the head chip, in which a semiconductor integrated circuit is mounted to the wiring substrate, the thermal head manufacturing method characterized by comprising: a step of joining a plurality of the head chips onto a wiring substrate forming plate from which a plurality of the wiring substrate can be obtained; a step of mounting a plurality of the semiconductor integrated circuits to the wiring substrate forming plate; a step of wiring the electrodes on the head chips to the semiconductor integrated circuits; and dividing the wiring substrate forming plates into a plurality of sections.
According to a nineteenth aspect of the present invention, in the eighteenth aspect of the invention, a thermal head manufacturing method is characterized in that the head chips are oriented in one direction, and juxtaposed as a plurality of rows longitudinally and laterally on the wiring substrate forming plate.
According to a twentieth aspect of the present invention, in the nineteenth aspect of the invention, a thermal head manufacturing method is characterized in that a part of the head chips are oriented in a direction perpendicular to the one direction to be joined.
According to a twenty-first aspect of the present invention, in any one of the eighteenth to the twentieth aspect of the invention, a thermal head manufacturing method is characterized in that the wiring substrate forming plate has elongated holes penetrating through the plate, and an inner peripheral surface of the elongated hole forms at least one end face of the wiring substrate.
According to a twenty-second aspect of the present invention, in the twenty-first aspect of the invention, a thermal head manufacturing method is characterized in that the wiring substrate forming plate is designed so that one inner peripheral surface of the elongated hole forms at least one end face of the plural wiring substrates.
According to a twenty-third aspect of the present invention, in the twenty-first or the twenty-second aspect of the invention, a thermal head manufacturing method is characterized in that the head chip extends across both peripheral edge portions of the elongated hole in the width direction, and is joined to only one of the peripheral edge portions.
According to a twenty-fourth aspect of the present invention, in the twenty-first or twenty-second aspect of the invention, a thermal head manufacturing method is characterized in that the head chip is provided so that a part of the head chip in the width direction is confronted with the elongated hole.
According to a twenty-fifth aspect of the present invention, in the twenty-first or twenty-second aspect of the invention, a thermal head manufacturing method is characterized in that the head chip is provided to be located on one of the peripheral edge portions of the elongated hole in the width direction and is not confronted with the elongated hole.
According to a twenty-sixth aspect of the present invention, a method of manufacturing a thermal head unit constructed so that a thermal head is held on a support member, the thermal head comprises a head chip having one surface on which heating elements and electrodes connected to the heating elements are provided, and a wiring substrate that is joined to the other surface of the head chip in a state that one end portion of the head chip in the width direction, which serves as a heating element forming portion, is protruded, and that mounts thereon a semiconductor integrated circuit connected to the electrodes, the thermal head unit manufacturing method characterized by comprising: a step of supplying an adhesive agent layer to a step difference portion of the support member, the support member having an upper step portion joined to the heating element forming portion, and the step difference portion recessed more deeply than a thickness of the wiring substrate; a step of placing the wiring substrate onto the adhesive agent layer provided to the step difference portion using as a reference a joining of the heating element forming portion to the upper step portion prior to hardening of the adhesive agent layer; and a step of subsequently hardening the adhesive agent layer.
According to a twenty-seventh aspect of the present invention, a method of manufacturing a thermal head unit constructed so that a thermal head is held on a support member, the thermal head comprises a head chip having one surface on which heating elements and electrodes connected to the heating elements are provided, and a wiring substrate that is joined to the other surface of the head chip in a state that one end portion of the head chip in the width direction, which serves as a heating element forming portion, is protruded, and that mounts thereon a semiconductor integrated circuit connected to the electrodes, the thermal head manufacturing method characterized by comprising: a step of providing a support member having an upper step portion joined to the heating element forming portion, and a step difference portion recessed more deeply than a thickness of the wiring substrate, and fixing the wiring substrate to the step difference portion using as a reference a joining of the heating element forming portion to the upper step portion while placing the wiring substrate to the step difference portion with a clearance therebetween; a step of supplying an adhesive agent to the clearance; and a step of subsequently hardening the adhesive agent layer.